1. Technical Field of the Invention
The present invention relates to a stator for rotary electric machines and a method of manufacturing the stator.
2. Related Art
In recent years, rotary electric machines used for electric motors and electric generators are required to be compact in size, to be able to output higher power, and to be of higher quality. In particular, when a rotary electric machine is mounted on a vehicle, the space in which the rotary electric machine is accommodated has become smaller, while it is demanded that the output therefrom is higher. In this circumstance, the conventional rotary electric machine has been provided by the structure for a stator whose stator coil is composed of a continuous winding (for example, refer to Japanese Patent Laid-open Publication No. 2004-320886).
For manufacturing the stator as disclosed by this Publication No. 2004-320886, a belt-shaped formed coil is wound to form a cylindrical stator coil. This cylindrical stator coil is then assembled with a stator core.
As disclosed by this publication, in cases where the stator coil is pre-formed and the stator core is combined (assembled) with the pre-formed stator coil, it is considerably difficult to have, with high precision, the stator coil accommodated in the slots of the stator core. For example, when the stator coil has been assembled with the stator core, the stator coil may protrude, at least partly, from the slots of the stator core in the radial direction of the stator. In general, the stator core faces a rotor with a very narrow gap (clearance). Hence, if the stator coil is left as being protruded, the coil may touch the rotor, whereby there may cause an electric short circuit due to flaking of the coat of the stator coil. It is thus necessary that the stator coil be accommodated in the stator slots without protrusion. For such complete accommodation of the stator coil, many man hours of workers in measurement and confirmation steps may be increased.
In particular, due to the following reason, there is a possibility that the stator coil might partly protrude from the slots of the stator core, when being assembled. In order to form a cylindrical stator coil, the coil wire being used should have a sufficient rigidity which still allows the coil wire to be bendable. For this reason, the coil wire can be bent sufficiently easily. Thus, during steps for forming the cylindrical stator coil, linear portions of a stator coil, which are mounted in the slots of the stator core, may be bent. A probability that the linear portions being mounted are forced to be bent partly or entirely is high. When the stator coil having such bent wire portions is assembled with the stator core, the bent wire portions raise their height in the slots, resulting in the bent wire portions possibly protruding, at least partly, from some slots of the stator.
In addition, after the cylindrical stator coil has been completed, this stator coil is assembled with the stator core. During this assembling step, the stator core inevitably presses the stator coil, resulting in that the stator coil is forced to receive a force directed toward the slot opening of the stator core. This force will cause the stator coil to deform toward the slot opening, which may also lead to a case that the stator coil protrude, at least partly in height, from some of the slots of the stator core.